Obesity caused by the abundance of food in recent years presents a problem. It has been recognized that obesity is a big factor to life-habit diseases such as heart disease, arterial sclerosis, hypertension, diabetes, or the like and, therefore, management of accumulated amounts of fat in the body is important to keep and improve one's daily health, which induces development of various body fat meters. As such a body fat meter, a body fat measuring device fabricated according to an impedance method to measure a bioelectrical impedance is known (Japanese Patent Publication No. 2002-369806).
On the other hand, a dog, cat, or the like being a small-sized animal raised as a pet have also an abundance of food and, there are many cases in which, for example, a pet owner feeling a sense of attachment to a pet wishes to properly manage pet body fat and to control feeding amounts so that these pets do not become fat and to maintain and improve the health of its dog, cat, or the like. Also, an impedance measuring tool is disclosed in which the measuring method of body fat according to the impedance method which has been applied to a human body is applied to domestic animals (Japanese Patent Publication No. 2002-253523). Furthermore, by having the problem that pet body hairs constitute an electrical insulator, some related technologies are disclosed in order to increase measuring accuracy which include technology to improve the shape of an electrode being in contact with a pet body (see Japanese Patent Publication No. 2003-144005), technology to make an electrolysis solution be held and supported between a contact region of a pet and an electrode (Japanese Patent Publication No. 2005-27661), and technology to use a measuring tool so that an electrode is in touch only with a root of limbs having little body hairs (Japanese Patent Publication No. 2004-254616).